National Save-the-Sea Turtle Foundation awards four $1000 Graduate Scholarships to Florida Atlantic University
Prof. Mike Salmon
Department of Biological Sciences
Florida Atlantic University at Boca Raton
The Department of Biological Sciences has once again been the recipient of five scholarships, totaling $4000, from the National Save-the-Sea-Turtle Foundation of Fort Lauderdale, Florida. These funds are used to support graduate research at the Master of Science and Doctoral levels. While in the past the Foundation has provided funding for projects involving marine turtles, this year the decision was made to support broader topics of research dealing with the conservation, management, or basic biology of marine fishes as well as turtles. This topical expansion also better reflects the interests of our department which in recent years, has expanded by hiring of several new and outstanding faculty in the various subdisciplines of marine biology. Their students can now apply and compete for these important scholarships. Below, I summarize their projects.
Shelby Creager started working with sharks because she was fascinated by the way shark skin felt, how it looked under the microscope, and how its structure varied at different locations on the shark’s body. She wanted to know whether shark skin structure influenced the ability of sharks to swim. That led to the development of an interest in materials testing.
Sharks have very unique skin properties, compared to other animals. It has been shown to contribute to shark swimming by acting as an external tendon that transmits forces along the animal’s body. The skin is covered in small teeth-like structures called dermal denticles. Denticle shape and size varies among species and along the length of the body. Previous studies on shark skin mechanics have been only been done on one species, so Shelby is interested in determining the mechanical properties of shark skin among several species, selected because of differences in how they swim. She will also examine regional differences in skin properties at twelve different locations on the shark’s body. Skin from the blacktip, the scalloped hammerhead, and the shortfin mako sharks will be stretched using a materials testing system until skin failure is reached. That’s the point at which the skin breaks. This system is similar to what an engineer use to test the properties of concrete or steel. For this study, she is calculating ultimate skin strength (force required to break the skin), stiffness (the skin’s ability to resist tension), as well as the size and number of denticles per mm2 for each sample. Denticle information will be correlated with ultimate strength and stiffness.

Mechanical testing may be of great interest to engineers, but why would this be important biologically? These findings will detail the mechanical properties and denticle shape and size from several species, and may provide inspiration for the development of new types of flexible propulsion systems and biologically inspired materials for construction.
Victoria (“Tori”) Erb first started studying sea turtles as a junior in college. She later volunteered at the Mote Marine Laboratory in Sarasota, Florida, documenting the location of sea turtle nests on neighboring beaches. Her responsibilities also included monitoring the nests throughout incubation, then determining how many hatchlings “made it” to the water. That experience peeked her interest in the plight of the hatchlings that didn’t make it. Tori’s thesis project focuses on measuring nest to surf mortality in loggerhead hatchlings, with particular emphasis on the sources of mortality for nests placed on Florida’s east coast. Those sources include predators (e.g., ghost crabs, raccoons, armadillos, foxes, coyotes, birds, and skunks), exposure to artificial light, and heat stress.

She will also conduct interviews with the permit holders who manage those beaches to obtain additional information about possible site-specific threats to hatchlings on the beach. Cooperation with local permit holders will be necessary to collect appropriate data during the duration of this study, while not interfering with ongoing studies. This project will be conducted on several east coast beaches, ranging from those fronting urban communities to others located adjacent to natural preserves. Cameras will also be used to identify the predators and to analyze the orientation of the hatchling tracks left behind when they crawled to the water, a useful measurement for identifying lighting problems. These data will create more accurate measures of current hatchling production that can be used to document changes in the future. Those kinds of measurements are crucial for formulating comprehensive plans needed to promote the recovery of these imperiled species.
Sarah Hoffman is interested in the different locomotor styles that marine organisms employ. Since water is so much denser than air, the resulting forces generated by the movements of fully aquatic organisms are amplified. As a student in the Integrative Biology program at Florida Atlantic University, Sarah is examining the role of control surfaces in sharks. Control surfaces, such as the pectoral fins, aid in vertical positioning with relatively little energy expenditure. The expanded head of hammerhead sharks (known as a cephalofoil) may also be a control surface and increase overall maneuverability. Though potentially advantageous in maneuvering, the cephalofoil prevents hammerhead sharks from rolling their bodies during turning as other pointy-nosed sharks do. So, Sarah is examining how hammerhead sharks initiate turns by recording their maneuvers with three-dimensional video cameras, then analyzing how the cephalofoil and pectoral fins are used during turning. Additionally, she will implant electrodes in the body musculature of these sharks to measure which muscles are used, and how they coordinate with other muscles during maneuvers. This comparative study will shed light on how different body forms of sharks accomplish complex movements, both in terms of their physiology and as well as their mechanics. The results are likely to be unique to each fish’s shape and in sharks (as well as many other fish species), shape matters!
Alexandra Lolavar studies how environmental factors, occurring inside the nest, determine sex ratios within the nests of marine turtles. Understanding this process is critically important for managing and conserving marine turtles so that the ratios of male to female hatchlings is appropriate and will be likely to promote the recovery of these threatened or endangered species.

Sea turtles have temperature dependent sex determination (TSD) - males are produced at cooler temperatures and females at warmer temperatures. While biologists remain confident of temperature’s role in sex determination, Lolavar’s studies have also identified moisture, in the form of rainfall, as another environmental factor that can modify sex ratios. Her experiments are designed to determine whether moisture alone, or the role of moisture as an agent of evaporative cooling, result in the production of more males. She is also interested in whether additional environmental factors, such as nest oxygen levels, also influence the ratios of males to females.

The fact that environmental factors have such an important impact on sea turtle development also means that the ongoing threat of climate change may be particularly worrisome. Sea turtle biologists anticipate that global warming might result in an overwhelming production of females; even less understood is how worldwide changes in precipitation that accompany global warming might also impact marine turtle sex ratios. These “unknowns” make studies such as Lolavar’s extremely important, as they can provide insights into how managers should respond if environmental changes begin to have adverse effects on marine turtle sex ratios.
Jake Lasala is interested in identifying the hidden elements of sea turtle behavior and population structure, those that determine the romantic relationships between males and females. The problem, from the perspective of an observer, is that how male and female marine turtles court and respond to one another occurs underwater, sometimes in deep water, and it’s only by the best of luck that human observers (let along those who are qualified biologists) get to witness what transpires. Even when they do see marine turtles mating, how can biologists be sure of the “result”? Mating may or may not be successful, especially when the offspring often number more than 100 hatchlings from a single nest. How many of those 100 are sired by a single male? If a female mates more often than once, a common occurrence in marine turtles, how many offspring are sired by different males? Many animals have similar (technically known as “promiscuous”) mating systems. In some of these species, all of the offspring are sired by the last male to mate with that female and none by those that mated with her earlier. Does that principle apply to marine turtles?

Lasala uses genetic markers from Mom and the hatchlings to answer these questions. The technique is essentially identical to the genetic methods used in lawsuits to determine paternity. Since each hatchling obtains half of their genes from mom and half from dad, you can use skin and blood samples from mom to identify her genes, and tiny amounts of blood from the hatchlings to identify her genes in each hatchling. Any unfamiliar genes found in the hatchlings must come from dad, and any different unidentified genes found in different hatchlings indicate that the hatchling had a different father.

By the end of the 2015 nesting season, Jake had sampled from over 135 nesting females and over 2,700 hatchlings from the three species that regularly nest on Florida’s beaches: the loggerhead, leatherback and green turtles nesting at three beach sites (Jupiter, Boca Raton and Sanibel, Florida). Each sample needs to be analyzed to determine paternity. Thus far, the results indicate that all species are promiscuous, but that loggerheads are more promiscuous than the other two species. Why that should be the case isn’t clear, and probably won’t be answered in this study. That’s a topic awaiting observations made by scientists who want to spend a lot of time underwater, watching the turtles make love. Jake, however, prefers to obtain his data by analyzing his tissue samples in the laboratory. To each, their own!

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